1. Field of the Invention:
The invention concerns carbohydrate fatty acid esters that are improved with regard to color and ease of handling, and a one-step process for preparing them.
2. Discussion of the Background:
Carbohydrate fatty acid esters and processes for preparing them are known. They can be prepared according to European Patents 0 132 293 and 0 132 941 by the transesterification of fatty acid esters of short-chained alcohols with a saccharide or a sugar alcohol. Processes are also known by which a direct esterification of carbohydrates is carried out with free fatty acids. Sorbitan fatty acid esters are prepared by direct esterification according to U.S. Pat. No. 4,297,290. According to this patent, anhydrosorbitol is first prepared from sorbitol with acid catalysis, and is then reacted with a fatty acid with alkaline catalysis. The color of the products is improved by treatment with activated charcoal, phosphoric acid, and diatomaceous earth.
Therefore, either an esterification and a transesterification are carried out, or an anhydrosugar is prepared and an esterification is carried out. These processes, therefore, require at least two reaction steps, with any optional treatment with activated charcoal, especially in the case of highviscosity products, representing another difficult process step.
According to German OS 31 19 553, carboxylic acid esters of anhydrohexitols are prepared by reacting hexitols, preferably sorbitol, with carboxylic acids using alkaline catalysis at 210.degree.-260.degree. C., and then treating the products with hydrogen peroxide.
However, this one-step process provides products that are not fully satisfactory for use as emulsifiers in high-quality cosmetics or foods with regard to clarity, color, and free-flow properties, especially when partially hydrogenated starch hydrolyzates are reacted with fatty acids.